Tracks left in 'unsafe' positionThe Australian Transport Safety Bureau found the points — movable rails which guide the wheels towards either the straight or the diverging track — were left in an "unsafe open position".

"The colour light point indicator system worked as designed by displaying a red indication when the points were unable to be detected and locked in a safe position," the bureau said in a 33-page report released today.

On departure from Adelaide, the freight train consisted of two locomotives hauling 32 wagons for a total length of 1693 metres and gross mass of 4343 tonnes.

A train braking calculator used by the Australian Rail Track Corporation says an 1800-metre-long freight train, three-quarter loaded and travelling at 110km/h needs at least 2220 metres to come to a complete stop.

At 11.13am, the train passed the Rawlinna location board, positioned about 2600 metres from the eastern end of the crossing loop points, travelling at 104km/h.

Using the same parameters, the calculator says about 2050 metres is needed on level track — the equivalent of about 15 seconds for the train crew to apply the brakes after passing the Rawlinna location board.

"It was likely a common practice for drivers to approach crossing locations without slowing when authorised for the main line," the ATSB report stated.

"Compounding this was the points enhancer sighting distance being less than the effective braking distance of trains travelling at line speed, thereby increasing the risk of overrun if not displaying a green aspect."

Alcohol, drugs and fatigue not a factorThe bureau noted in its report that the crew van did not meet requirements because "the occupant could not access any escape paths without external assistance and additional equipment".

The report also found the condition and serviceability of the train "did not affect its handling at the time of the occurrence" and was not considered a factor in the derailment.

Alcohol, drugs and fatigue were also ruled out as a possible factor, with the driver and co-driver both highly experienced.

The driver was wearing prescribed sunglasses — the lenses were tinted grey and not polarised — supplied by Pacific National.

The driver underwent a medical assessment in May 2015, including vision and colour blindness testing, and was declared fit for duty without restriction.

"Given the driver's fitness for duty and no evidence of colour interference from a grey tint, it is likely that the prescription sunglasses worn by the driver did not affect the colour transmission of the red indicator," the report stated.

"It is plausible that other factors such as distance, heat haze, and expectation may affect the interpretation of a red indicator."

Trains rarely slow down for crossingsThe bureau also examined recorded data to understand the common behaviour of trains approaching crossing locations.

It found in the seven days leading up to the incident, 79 per cent of daytime trains passing through Rawlinna did not slow down before the effective sighting of the enhancer light.

Investigators on site measured about 1200 metres sighting of the eastern enhancer light from ground level, which is dependent on the time of day, weather, heat haze, direction of sun, and other environmental conditions.

Following the incident, Pacific National conducted an audit of enhancer sighting distances between Cook and Kalgoorlie, both east and west bound.

The results of the audit found that about 50 per cent of locations exhibited effective sighting distances of less than 2000 metres in daylight hours.